Signaling system



July 14, 1931. w. H. T. HOLDEN SIGNALING SYSTEM Filed April 22, 1926INVENTVORI ffi vldem ATTOPNEY connects Patented July 14, 1931 UNITEDesrsnr rice".

XVILLIAIVI' H. T. HOLDEN, OF BROGKLYN; ,NE-WYOEK, ASSIGIT 0111 TO AMEBtICA'N EFF-LE PHONE AND CQMPANY; A3 C'OBPORATGJGN' 01' NEW YORKSIGNALING- SYSTEM Application filed April 22,

This invention relates to signaling sys tems, and. moreparticularly toarrangementsin such, systems, including; aplurality of vacuum. tubesinterconnecting; anincom- Eng circuit and, an:outgoingcircuiu so'thatthe circuits associated: with said. vacuum tubes may be energized byasource ofrectie fled; alternating current:

Heretofore, it has been the practice: to onnect a, plurality of vacuumtubesto a plurality of batteries known as A, B andflG batteries fortheenergization of the circuits; associated with said vacuum:- tubes; The Abatteries were employed for; bringing the cathodesof'thevacuumtubesvtothe proper. electron emitting: temperature. The Bbatteries were employed for bringing the anodes or seid'vacuum tubes tosuitable potentials Withrcspect to the cathodes, and the C batterieswere employed for providthe necessary bias for the grids of saidvacuumi'tubes.

It has also bcc-n the practice to connect a single B? battery totheanodes of'tWo or' more vacuum tubes whichgwerc operated-a the samepotentials, these anodes being con nected to the B battery by'means of"a; connnon lead. The presence'of; the impedanceot this iced and of: theB battery, both common to the plate circuits; of the several. vacuumtubes, ended to give rise to the phenomenonknown as singing whichgenerally interfered with; the favorable transmission of'si gnals.

It is on objec-tio'f this inventiontopro vide arrangements foreliminating; the use of the A, B and"-G'battcries. for estab lishing thenecessary operating potentials for aplurality of vacuumtubes, andtoprovide instead: thereof means connected'to a source of, alternatingcurrent; through a rectifier, forv obtaining equally; operativepotentials.

It is another object of thisinvention to plurality of vacuum tubes of asignaling-system toeplurality of resistances which are in. seriesrelationship With a: source of electromotive forcepso that eachvacuumtube. h as: one resistance included 1 in its-input circuit, and:snotherresistance included in; its output circuit, the drop in. potentialacross-- eachresistance being of the proper magnitude to energize the.associated circrut.v

It i s-another object of this inventicn to provide arrangements forsubstantially liminating the effect. know-n as singing? which arisesfrom. theuseof; common. im pedonce pathsin the system.

' While the-natureof theinvention-Willbe peintectout; withparticularity; in the appended; claims, the invention.- itself, both, asto its funthe-r objects: and featureswill be better understood fromthe"detailed descrip tion hereinafter following when read in con nectionwith. the accompanying; drawingsho-w-ing only one embodiment of theinvem tion.,

In the drawing there is shown a system which includes: a receivingantenna RA; and" oscillator O; a detector D two stagesof amplification,-including amplifiers A andA another detector-D other stagesoramplification including amplifiers-A Al A undr'li andia translatingdevice such as aslouclspeaker A; source of alternating, current, preferably 2t llll-Voltsixty cycle, house lighting cirr cuit isdcsign ated bythereference character signaling This; source of alternating current iscon nected with 1 the primary Winding 2 ot a, transformer- T] y closingswitch, The secondary 0f the transtormerT- comprisesthreewindings4:, 5ands, windings 4: andfi being; low voltagewindings; and windingbbeing ahigh'voltage- Winding, The refer= ence chn-racten R1 represents itrectifier of the electron type having an r anode and a cethode, but itis to be distinctly understood that. any other: rectifier art 'beeiinplc 'ed instead thereof Within the scope of this-invention;

A simple series circuit includes the anode of the rectifierWhich-isgrounded theresista-nce R the cathode of the oscillator O,resistance R the resistance: R cathode of the detector- D the resistanceR re+ sistence R the cathode of the amplifier A the resistance R theresistance R the cathode of: the amplifier A Well known in the the resthe transformer T the amplifier and one-half of the secondary winding 6of the transformer T resistances, R and sistance R the cathode of thedetector D the resistance R the resistance R the cathode of theamplifier A the resistance R the resistance R the cathode of theamplifier A the resistance R the variable resistance R an inductance 7,the secondary winding 5 of the transformer T and the cathode of therectifier R. The resistances R and R and the windings 8 and 9 of atransformer T are in the input and output circuits of the oscillator 0,respectively. The resistances R and R are included along with thereceiving antenna RA and the winding 10 of the transformer T and theprimary winding of the transformer T in the input and output circuits ofthe detector D respectively. The resistances R and R are included alongwith the secondary winding of the transformer T and the primary windingof a transformer T. in the input and output circuits of the .amplifier Arespectively. The resistances It and R are included along with thesecondary winding of the transformer T and the primary winding of thetransformer T in the input and output circuits of the amplifier Arespectively. The resistance R is included along with the primarywinding of the transformer T in the output circuit of the detector D TheR are included along with the secondary winding of the transformer T andthe primary winding of the transformer T in the input and outputcircuits of the amplifier A respectively. The resistances R and R areincluded along with the secondary winding of the transformer T and theprimary winding of a transformer T in the input and output circuits ofan amplifier A respectively.

The secondary winding l of the transformer T is used for heating thecathode of the rectifier R, whereas the secondary winding 6 of thetransformer T is used for heating the cathodes of the amplifiers A and Awhich are in parallel relationship with each other. Thus, the cathodesof the rectifier R and of the vacuum tubes of the last stages ofamplification in the signaling sys tem are supplied with alternatingcurrent for furnishing the necessary energy there for. Let it be notedthat it is one of the features of this invention to heat the cathodes ofthe vacuum tubes in the last stages of amplification in a signalingsystem by alternating current. The noise produced 1n the system by theuse of alternating current to heat the cathodes in the last stages ofamplification is practically negligible.

A resistance R is common to the input circuits of the amplifiers A and Aeach of these input circuits including the resistance R one-half of thesecondary winding of the grid and cathode of If, by virtue of the size,the diameter and the material employed for the various cathodes, any ofthe cathodes would receive too much current, it is within the scope ofthis invention to connect resistances to shunt these cathodes to therebylessen the current flowing through these cathodes.

The inductance 7 and and C comprise a a low-pass filter. This filter isconnected to the rectifier R for rendering the series circuit, whichincludes the resistances R to R inclusive, as free from alternatingcurrent components as possible. Inasmuch as the cut-off frequency ofthis filter, which may be, for example, 30 cycles, is lower than thefrequency of the source of alternating current 1, no frequency of thesource 1, or produced therefrom by the action of the rectifier, will bebelow the cut-off frequency of the filter, and therefore the seriescircuit which includes resistances R to R will be substantially freefrom alternating current components.

The resistances R to R inclusive, are of such magnitudes that thedifference in potential across each of said resistances is sufiicient toprovide the proper potential for each associated circuit. Thus, thedifference in potential across each of the resistances R and R R and R Rand R R and R will supply the necessary potentials for the input andoutput circuits, respectively, of the oscillator O, the detector D theamplifier A and the amplifier A The detector D has a resistance R and acondenser C in parallel with each other and in series with the secondarywinding of the transformer T in the input circuit thereof. Theresistance R in the output circuit of the detector l) supplies thepotential necessary to operate the output circuit thereof. Thedifference in potential across each of the resistances R and R R and Rsupply the necessary potentials for the input .and output circui s,respectively of the amplifiers A and A The condenser C connects thepoint com mon to resistances R and R to the grounded anode of therectifier R. The condenser C connects the point common to resistances Rand R to the grounded anode of the rectifier R. Furthermore, thecondenser C connects the point common to the resistances R and R to thegrounded anode of the rectifier R. It will be understood, however, thatother condensers such as C C C and C shown in dotted lines, may beemployed in this in-' vention for bridging various points in the seriescircuit including resistances R and R to the grounded anode of therectifier B.

These condensers G to C inclusive, are employed for substantiallyeliminating the effect known as singing which arises from the use ofcommon impedance paths. It will be understood, however, that it iswithin the two condensers C filter which is preferably.

binations of inductances and condensers in place of the condensers shownherein to accomplish this object.

The windings 8 and 9 of the transformer T in the input and outputcircuits, respectively, of the oscillator O, are coupled together. Avariable condenser C is connected across the terminals of these windingsso that the circuit including the windings 8 and 9, and the condenser Cmay have negligible reactan'ce at a frequency which is characteristic ofthe oscillator O.

The frequency of this oscillator, which may be, for example, 660kilocycles, beats with the carrier frequency received by the receivingantenna RA on which are superposed one or both side bands correspondingto low frequency signals. A variable condenser C is connected to thereceiving antenna BA to render the antenna selective to a particularfrequency such as, for example, 610 kilocycles. The detector D beats thefrequency of the oscillator O with the frequency received by thereceiving antenna RA, on which are superposed side bands correspondingto low frequency signals. Consequently an intermediate frequencyresults, which has a frequency equal to the difference between thefrequency of the oscillator O and the frequency received by thereceiving antenna RA. This intermediate frequency will also havesuperposed thereon the side bands received by the receiving antenna RA.Condensers C and C are bridged across the terminals of the primary andsecondary windings of the transformer T so as to by-pass all frequenciesexcept the intermediate frequency upon which the side bandscorresponding to the low frequency signals are superposed.

The intermediate frequency and its side bands are amplified by theamplifiers A and A This intermediate frequency and its side bands arethen impressed on the in put circuit of the detector D and, as is wellknown in the art, there will appear in the output circuit of thedetector D signals corresponding to the side bands superposed on thecarrier received by the receiving antenna RA. A condenser C is connectedbetween the anode and cathode of the detector D in order to bypass allfrequencies above the range employed as low frequency signals. These lowfrequency signals are then amplified by amplifiers A A A and A in amanner well known in the art. Condensers C and C are connected betweenthe anodes of amplifiers A and A respectively, and the loud speaker S,so that only the low frequency signals may pass to the loud speaker S.

In my copending application, Serial No. 70,157, filed November 19, 1925,I have disclosed and claimed an arrangement including: a source=ofrectified: current: connected to a plurality of 'resist'ances set up soas to supplythe potentialsrequired to energize the circuits ofaplurality of vacuum tubes-.

Vfhile the invention has been disclosed in one particular signalingsystem, it is-tobe understood that it is capable of embodiment in othersignaling systemsand in widely varied organizations of such systemswithout departing from the spirit of the invention and the scope. ofthe-appended claims.

What is claimed is:

1. In a radio receiving system, in combination, a plurality ofthree-electrode vacuum tubes, aplurality of transformers interconnectingsaid vacuum tubes, aasource of alternating current, a rectifier, and aplu rality of resistances in series relationship with eachother, saidresistances beingsupplied with current rectified'by said rectifier,two-of said resistances being provided for each of" the various vacuumtubes, one of which is connected to the input circuit of eachva'cuumtube and the'other to the out put circuit of each vacuum tube,the-two resistances associated with any one of the vacuum tubes beingdifferent from. those associated with: any of the other vacuum tubes,said resistances applying the: required potentials tothe circuitsof saidvacuum tubes 2. In a radio receiving system, in com bination, source ofalternating current, means for rectify-ing the alternating currentthere-from, a plurality of vacuum tubes, a plurality of" transformersinterconnecting saidvacuumtubes, and a pl urality ofresistances inseries relationship with each. other for furnishing from the rectifiedcurrent the potentials required by said vacuum tubes, each of:saidvacuum tubes being provided with two-of said resistances, thetlworesista-nces associated with any one of 'the vacuum tubes beingdifferent from those associated With any of' the other vacuum t'ubes,each of theinput circuits of thevarious vacuum tubes, including one ofsaid resistances, each oftheoutput circuits 'of the various vacuum tubesincluding another of said resistances.

3. A signaling system comprising a plurality of vacuum tubes, aplurality of transformers interconnecting said vacuum tubes, a pluralityof resistances in series relationship with each other, said resistancesbeing separated into pairs, each pair being provided for one of thevarious vacuum tubes, one of the resistances of each pair beingconnected to the input circuit of the corresponding vacuum tube and theother to its output circuit, means for sending direct current throughsaid resistances, said resistances being employed for supplying thepotentials required by the input and output circuits of said vacuumtubes, and means for substantially eliminating common impedance pathsfor signals passing through the system.

4. A system for receiving and detecting low frequency signals modulatedon a high frequency wave comprising a plurality of three-electrodevacuum tubes, a plurality of transformers interconnecting said vacuumtubes, a source of alternating current, a rectifier, said rectifierrectifying the alternating current, and means for supplying the properpotentials for operating said vacuum tubes from current rectified bysaid rectifier, said means consisting of a plurality of resistances inseries relationship with each other, two of said resistancescorresponding to each of said vacuum tubes, one of which is connected tothe input circuit of each Vacuum tube and the other to the outputcircuit of each vacuum tube, the two resistances connected to therespective input and output circuits of any one of the vacuum tubesbeing distinct from those connect-ed with the input and output circuitsof any of the other vacuum tubes, each resistance having a predetermineddrop in potential across its terminals.

5. In a radio receiving system, in combination, a plurality ofthree-electrode vacuum tubes and transformer coupling meansinterconnecting said vacuum tubes, a source of rectified alternatingcurrent, means comprising a plurality of resistances connected in seriesfor supplying the proper potentials for operating said vacuum tubes fromsaid source of rectified alternating current, two of said resistancesbeing provided for at least one of the vacuum tubes, one of whichresistances is connected to the input circuit of said vacuum tube andthe other to the output circuit of said vacuum tube, the said tworesistances associated with said one of the vacuum tubes being differentfrom those associated with any of the other vacuum tubes.

In testimony whereof, I have signed my name to this specification this21st day of April, 1926.

WILLIAM T. HOLDEN.

